1. Field of the Invention
The present invention relates to a satellite communication system of the SCPC method using a voice activation, and relates to a center station used in order to carry out such a satellite communication system.
2. Description of the Related Art
In the conventional satellite communication system of the SCPC (Single Channel Per Carrier) method, when an user A communicates with an user B, an user C can communicate with neither the user A nor the user B. Thus, when the user A communicates with the user B, the user C must wait until the communication terminates in order to notify the user B of information.
As above described, in the conventional satellite communication system of the SCPC method, when a person communicates with another person, no one can communicate with the person until the communication terminates. In other words, the conventional satellite communication system has a possibility that it is impossible to notify an user of emergency information, such as disaster information.
Additionally, when a modulator-demodulator (modem) for a control signal such as a pilot signal (a modulator-demodulator for line control) is provided in a VAST (Very Small Aperture Terminal) station in a satellite communication system in addition to the modem for the telephone line, the line can be forcibly cut off by using the control signal. However, when the line is forcibly cut off, an user tends to redial, since the user does not understand the reason of the cut-off. Further, since it takes a cost to implement the VAST station, it is not a wise plan to adopt this approach in order to makes the emergency communication possible.